The invention concerns a method and an apparatus which is especially advantageous for its performance in the thermal longitudinal parting of rectangular metal plates, in particular of cut-to-length continuous casting plate slabs while the metal plates rest on supports which run crosswise to the longitudinal direction of the parting. In the cross-parting of steel, cast as a continuous slab, or of NE-metals, the thermal separation on the basis of oxygen-flame cutting or plasma-flame cutting serves the preparation for the rolling which follows, whereby the cross-parting determines the length of, for instance, the coil weight of the tin sheeting to be rolled. Compared with that, the conditions, when parting metal slabs longitudinally, present themselves differently because in the latter case the desired width of the tin sheeting to be rolled out is determined. In recent years the aim was to increase the production rate in continuous casting through increasing the batch weights and through larger slab widths. Wider slabs do allow for a more economical production of casting products under maximal exploitation of the slab-casting apparatus. However, the wider slabs must be reduced to the existing first-pass cross sections of the rolling mills, the width dimensions of which in turn go necessarily by the widths of the tin sheeting which are required in the subsequent procedure.
It is well-known (DE-AS No. 27 10 564) how, in order to fulfill this requirement, to move the cutting arc relative to the plate slab when parting crosswise, in which case, according to this suggestion vis-a-vis parting lengthwise the only difference is that the plate slab is at rest. The well-known longitudinal parting procedure requires, however, special steps for the protection of the supports which pass in crosswise direction to the longitudinal parting direction. Therefore, a diversified formation is required of the existing supports which go crosswise to the longitudinal parting direction. At first, longitudinally driven rolls cause the transportation of the plate slabs. These rolls must be able to swing out in order not to be destroyed during the flame cutting. Further, crosswise-passing rigid plate slabs are provided which have to have so-called burn point openings for the path of the cutting arc. The burn point openings which are arranged in the path of the cutting arc result in a slit-like burn canal, the length of which corresponds to the length of the plate slabs, for instance 8 m and more, turns out to be very extended. A further disadvantage is that the slag and an increased amount of gas must be carried away from the long burn canal. Besides, the burning canal is firmly built-in and does not allow for any adjustment to changing the widths of the plate slabs to be parted longitudinally.
The invention is based on the task to simplify the known method, and based on that to create a better protected apparatus with less expenditure.
This task is solved in accordance with the invention by moving the metal slabs in longitudinal parting direction vis-a-vis the cutting arc which is motionless in the longitudinal parting direction and which is in a given case movable crosswise to the longitudinal parting direction only because of corrections in width conditional on deviations in width or through skewed position of the metal slabs, and by carrying off between two supports the slag collected at some point crosswise to the longitudinal parting direction between two supports. This proposal follows neither the principle of crosswise parting, in which case the continuously cast slab is moved by the pouring velocity which is followed by the cutting arc, nor does it follow the known principle where the continuous-cast plate slab is at rest. Consequently, it is advantageous that neither swing-away support rolls nor a relatively long burn-canal are necessary but that a burn-canal results naturally between the two existing support rolls. Accordingly, the burn-canal is short and the collected burn slag may be removed via a short passage. Furthermore, there is a resultant decrease in the volume of gas-exhaust and accordingly less power for the drive of the gas-exhaust. Another advantage of the invention lies in the fact that heavy crosswise-slidable slab centering machines are avoided, which are replaced by control arrangements which move the much lighter cutting arc installations. A further advantage lies in the possibility of changing the width-program without displacing the burn-point openings, i.e., to insert partings of 1/2, 1/3, 1/4 and the like for short runs.
An increased cutting performance may now be achieved after a further improvement of the invention, in that at least two metal slabs are moved relative to motionless cutting arcs which are at any given time spaced in the longitudinal parting direction. The doubling of the cutting capacity leads to an increased yield in cut goods and to an increased performance in comparison with cutting machines which run counter and thereby necessarily impede each other on encounter.
The performance of longitudinal parting is increased by an additional proposal in method when at a given time a metal slab is being cut only partially in the longitudinal direction, the cutting arc switched off afterwards, and this same metal slab is completely parted under a cutting arc which is pre-positioned in the longitudinal parting direction at a distance of more than the length of a slab, while the following metal slab is again parted, in longitudinal direction, only partially with the cutting arc again switched on.
The apparatus for the application of the invented method is designed in such a way that a cutting arc is provided between two rigidly arranged roller-bed rolls supporting the metal slabs along their full width. The cutting machine is motionless in the longitudinal parting direction and may be adjusted crosswise to the longitudinal parting direction. A pair of driving rolls are mounted adjacent the cutting machine. A conveyor duct for the resultant slag is provided, arranged crosswise to the longitudinal parting direction under the cutting machine, and a gas-exhaust pipe is connected to the conveyor duct. No swing-away rolls or additional supports are needed. The cutting machine, which is only movable crosswise, needs simpler electric conductors and conductors for the means of cutting. In view of the width of the slab, the conveyor duct has relatively short dimensions and requires a smaller intake of energy. The exhauster performance of the gas-exhaust pipe is also less.
The transport of the uncut metal slabs, as well as the pieces cut and longitudinally parted, causes no problem, in that two cutting machines are tandem-joined, with a distance between the longitudinal parting direction at least as large as the maximal length of a metal slab.
A pair of driving rolls is positioned in front of the first cutting machine and a second pair of driving rolls is positioned behind the second cutting machine in longitudinal parting direction. The distance between the first cutting machine and its respective pair of driving rolls is at any time smaller than the uncut length of a minimal metal slab length while the distance between the second cutting machine and its respective pair of driving rolls is smaller than the cut length of a minimal slab after leaving the first cutting machine.
The crosswise movability required for the lateral corrections of the cutting machine may be used for an additional function, in that the cutting machine is adjustable crosswise to the longitudinal parting direction to provide for various parting widths of the cut slabs.
In addition, the short length of the slag conveyor path advantageously permits the conveyor duct to consist of a vibrating chute. To allow for lateral correction, as well as adjustment for various parting widths, lateral tracing devices are provided for tracing the vertical slides of the metal slabs which determine their width. The cutting machine is arranged to be motionless in the longitudinal parting direction, and the control of the crosswise drive of the cutting arc is geared towards an even distribution of the deviations onto the width of the pieces parted longitudinally.
While the long cutting path on cutting machines which are moved in cutting (transverse) direction require increased input for sound containment, the invention permits the cutting machine, which is stationary in longitudinal parting direction, to be arranged in a soundproof casing corresponding to the size of the cutting machine. The invention also avoids movable attachments and provides a rigid striker bar on at least one side of the roller bed at the level of the metal plate bar thickness.
A high cutting performance is attained while using less space when several longitudinal parting paths are arranged parallel next to each other, connected via a device pulling in transversal direction.
An example embodiment is shown in the drawing and is described in more detail below.